1. Field of the Invention
Embodiments of the present invention generally relate to a method and apparatus for an adaptive gain control Unit, and more specifically, a gain adaptation and noise suppression for a stethoscope.
2. Description of the Related Art
Stethoscopes that incorporate a digital signal processor to process signal recorded by a stethoscope sensor before conveying the processed signal to the user, are gaining popularity. The advantage of using the digital signal processor is the ability to provide amplification and noise reduction, along with visualization and other signal analysis abilities.
Active noise removal in digital stethoscopes is accomplished by using 2 or more additional sensors to pick up the ambient noise and using an adaptive filtering algorithm to remove the noise from the signal picked up by the main sensor. The issue with such an approach, apart from the need for multiple sensors, is that it could introduce musical noise artifacts in the noise suppressed signal.
Another approach to removing noise is the use of wavelet de-noising. Such an approach may, due to the similarity between the time-domain shape of the heart sound and the shape of the wavelets, facilitate coding the waveform into the wavelet domain using only a few coefficients, and then, reconstruct the waveform to remove noise.
These solutions provide linear amplification, rather than adaptive gain. The level of amplification may be set by the user. As such, most current digital stethoscopes provide a linear amplification, as opposed to adaptive gain, that could lead to saturation and clipping of the waveform, if the signal intensity were to increase. Other solutions use a digital signal processor to perform automatic control of amplification and adaptively removing noise. However, such solutions use different methods to achieve different functionality.
Therefore, there is a need for a method and/or apparatus that would for improving the functionality of a digital stethoscope, while utilizing a single method and the same system.